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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 254 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

NameDateTime takenScore ___ / 40
  1. 1.The two interior opposite angles of a triangle are 20° and 71°. What is the exterior angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 36° and 57°. What is the exterior angle (in degrees)?
  3. 3.Can a triangle have sides of 19 cm, 8 cm and 12 cm? (a) No (b) Yes
  4. 4.The two interior opposite angles of a triangle are 29° and 20°. What is the exterior angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 70° and 25°. What is the exterior angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 8 cm, 19 cm and 8 cm? (a) Yes (b) No
  8. 8.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  9. 9.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  10. 10.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 11 cm, 5 cm and 5 cm? (a) Yes (b) No
  13. 13.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 49° and angle B = 37°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 63° and angle B = 27°. What is angle C (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 77° and 80°. What is the exterior angle (in degrees)?
  23. 23.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 72° and 71°. What is the exterior angle (in degrees)?
  25. 25.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 10 cm, 5 cm and 9 cm? (a) No (b) Yes
  29. 29.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 82° and angle B = 44°. What is angle C (in degrees)?
  31. 31.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  33. 33.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 4 cm, 2 cm and 4 cm? (a) No (b) Yes
  38. 38.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?

Answer key

  1. 91
  2. 93
  3. Yes
  4. 49
  5. 95
  6. 60
  7. No
  8. 90
  9. 8
  10. 20
  11. 74
  12. No
  13. 48
  14. 38
  15. 45
  16. 70
  17. 27
  18. 94
  19. 15
  20. 32
  21. 90
  22. 157
  23. 24
  24. 143
  25. 37
  26. 90
  27. 22
  28. Yes
  29. 77
  30. 54
  31. 15
  32. 77
  33. 35
  34. 22
  35. 73
  36. 17
  37. Yes
  38. 26
  39. 61
  40. 120

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